Power cable of great lengths, on the order of 10,000-15,000 feet, are used in seismic testing operations. In particular, this cable is suspended in an oil well and has seismographic analytical equipment at the end to assist in locating oil bearing rock formations. Typically, this power cable is fed into the open well and removed therefrom via opposed tractor feeding mechanisms comprising a pair of spaced parallel belts having a series of cleats thereon which grip diametrically opposed sides of the cable. An example of this feeding device is disclosed in U.S. Pat. No. 3,285,485 to Slator, the disclosure of which is hereby incorporated herein by reference.
While many attempts have been made to provide optimum power cable for use in seismic testing, numerous disadvantages are present in these prior power cables. Thus, many of these cables are not self-supporting and thus require additional tubing or other supports thousands of feet long. In addition, many of these prior power cables are extremely heavy, and thus are difficult to work with and costly to make. Moreover, many of these power cables do not have significant resistance to transverse compressive forces created by the normal forces of the cleats on the tractor feeding devices.
Examples of these prior power cables are disclosed in the following U.S. Pat. Nos.: 2,690,984 to Crandall et al; 4,262,703 to Moore et al; 4,315,099 to Gerardot et al; 4,374,530 to Walling; 4,490,577 to Neuroth; 4,572,926 to Ganssle et al; and 4,644,094 to Hoffman, the disclosures of which are hereby incorporated herein by reference. In addition, prior power cables are disclosed in U.K. Pat. No. 1,250,823 to Spencer and European patent applications 0060061 to Walton and 0066910 to Baldoni. Power cables are also disclosed in pending, commonly assigned U.S. patent applications Ser. No. 896,011 filed on Aug. 13, 1986 in the names of Ernest G. Hoffman and David H. Neuroth, and Ser. No. 937,009 filed on Dec. 2, 1986 in the names of Ernest G. Hoffman and David H. Neuroth.